You can now Change or Add Office 365 Group Emails using Office 365 PowerShell.  The script below can be used.  This abilty has been added recently to Office 365.  You simply connect to Office 365 using Global Administrator and then use he syntax to do the updates.  The script below is only updating a single item.  With minor updates you can update emails using CSV or text file.  



$Creds = Get-Credential -Message “Please enter Office 365 Global Admin Credentials” 
$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri -Credential $Creds -Authentication Basic -AllowRedirection 
Import-PSSession $Session 
$AllGroups = Get-UnifiedGroup -Filter * 
#Getting first group just for checking.   
$FirstGroup = Get-UnifiedGroup -Identity $AllGroups[0].Id 
#{Add=”<Type>:<emailaddress1>”,”<Type>:<emailaddress2>”,…; Remove=”<Type>:<emailaddress2>”,”<Type>:<emailaddress2>”}. 
$EmailAdded = @{Add=””} 
Set-UnifiedGroup -Identity $FirstGroup.Id -EmailAddresses $EmailAdded -Verbose